/*
 * @(#)InputParser.java
 *
 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
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 *
 * You acknowledge that this software is not designed or intended for use in
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 */

package org.wso2.balana.ctx;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.wso2.balana.ParsingException;

import java.io.File;
import java.io.InputStream;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

/**
 * A package-private helper that provides a single static routine for parsing
 * input based on the context schema.
 * 
 * @since 1.0
 * @author Seth Proctor
 */
public class InputParser implements ErrorHandler {

	// the schema file, if provided
	private File schemaFile;

	// the single reference, which is null unless a schema file is provided
	private static InputParser ipReference = null;

	// the property string to set to turn on validation
	private static final String CONTEXT_SCHEMA_PROPERTY = "com.sun.xacml.ContextSchema";

	// the logger we'll use for all messages
	private static Log logger = LogFactory.getLog(InputParser.class);

	// standard strings for setting validation

	private static final String JAXP_SCHEMA_LANGUAGE = "http://java.sun.com/xml/jaxp/properties/schemaLanguage";

	private static final String W3C_XML_SCHEMA = "http://www.w3.org/2001/XMLSchema";

	private static final String JAXP_SCHEMA_SOURCE = "http://java.sun.com/xml/jaxp/properties/schemaSource";

	/**
	 * Look for the property that names the schema, and if it exists get the
	 * file name and create a single InputParser instance
	 */
	static {
		String schemaName = System.getProperty(CONTEXT_SCHEMA_PROPERTY);

		if (schemaName != null)
			ipReference = new InputParser(new File(schemaName));
	};

	/**
	 * Constructor that takes the schema file.
	 */
	private InputParser(File schemaFile) {
		this.schemaFile = schemaFile;
	}

	/**
	 * Tries to Parse the given output as a Context document.
	 * 
	 * @param input
	 *            the stream to parse
	 * @param rootTage
	 *            either "Request" or "Response"
	 * 
	 * @return the root node of the request/response
	 * 
	 * @throws ParsingException
	 *             if a problem occurred parsing the document
	 */
	public static Node parseInput(InputStream input, String rootTag)
			throws ParsingException {
		NodeList nodes = null;

		try {
			DocumentBuilderFactory factory = DocumentBuilderFactory
					.newInstance();
			factory.setIgnoringComments(true);

			DocumentBuilder builder = null;

			// as of 1.2, we always are namespace aware
			factory.setNamespaceAware(true);

			if (ipReference == null) {
				// we're not validating
				factory.setValidating(false);

				builder = factory.newDocumentBuilder();
			} else {
				// we are validating
				factory.setValidating(true);

				factory.setAttribute(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA);
				factory.setAttribute(JAXP_SCHEMA_SOURCE, ipReference.schemaFile);

				builder = factory.newDocumentBuilder();
				builder.setErrorHandler(ipReference);
			}

			Document doc = builder.parse(input);
			nodes = doc.getElementsByTagName(rootTag);
		} catch (Exception e) {
			throw new ParsingException("Error tring to parse " + rootTag
					+ "Type", e);
		}

		if (nodes.getLength() != 1)
			throw new ParsingException("Only one " + rootTag + "Type allowed "
					+ "at the root of a Context doc");

		return nodes.item(0);
	}

	/**
	 * Standard handler routine for the XML parsing.
	 * 
	 * @param exception
	 *            information on what caused the problem
	 */
	public void warning(SAXParseException exception) throws SAXException {
		if (logger.isWarnEnabled())
			logger.warn("Warning on line " + exception.getLineNumber() + ": "
					+ exception.getMessage());
	}

	/**
	 * Standard handler routine for the XML parsing.
	 * 
	 * @param exception
	 *            information on what caused the problem
	 * 
	 * @throws SAXException
	 *             always to halt parsing on errors
	 */
	public void error(SAXParseException exception) throws SAXException {
		if (logger.isErrorEnabled())
			logger.error("Error on line " + exception.getLineNumber() + ": "
					+ exception.getMessage());

		throw new SAXException("invalid context document");
	}

	/**
	 * Standard handler routine for the XML parsing.
	 * 
	 * @param exception
	 *            information on what caused the problem
	 * 
	 * @throws SAXException
	 *             always to halt parsing on errors
	 */
	public void fatalError(SAXParseException exception) throws SAXException {
		if (logger.isErrorEnabled())
			logger.error("FatalError on line " + exception.getLineNumber()
					+ ": " + exception.getMessage());

		throw new SAXException("invalid context document");
	}

}
